Back contact solar cell, assembly and photovoltaic system

Abstract

The invention discloses a back contact solar cell, an assembly and a photovoltaic system, and relates to the field of silicon solar cells. Specifically, the back contact solar cell comprises a silicon substrate, a first doping layer, a second doping layer, a positive electrode grid line, a negative electrode grid line and a first PAD part. The second doping layer is in composite contact with the first doping layer at a preset position to form an electric leakage composite contact structure; each group of first PAD parts comprises a first PAD point and a second PAD point, the first PAD point is electrically connected with at least one positive grid line, and the second PAD point is electrically connected with at least one negative grid line; the positive grid line electrically connected with the first PAD point extends along a second direction, and the extension distance is l1; the distance between the first edge and the second edge is L, and l1 / L is greater than or equal to 0.9; the negative grid line electrically connected with the second PAD point extends along a second direction, and the extension distance is l2; l2 / L > = 0.9. By implementing the method, the hot spot effect can be accurately represented at the battery end.

Description

Technical Field

[0001] The present invention relates to the field of silicon solar cells, and in particular to a back-contact solar cell, a component and a photovoltaic system. Background Art

[0002] When one or more solar cells (or slices) in a photovoltaic module are partially or completely shielded, the shielded solar cells (slices) will show a voltage reverse bias characteristic and become a load, consuming the power generated by normal solar cells, thereby generating a large amount of heat, making the temperature of the solar cell higher, which is generally referred to as the hot spot effect. In the prior art, in order to solve the hot spot problem, a diode is generally connected in reverse parallel at both ends of the string unit to reduce the current of the shielded solar cell and weaken the hot spot effect. However, this parallel diode will produce power loss. In order to solve this problem, a feasible idea is to directly form a leakage composite contact structure on the solar cell (see CN117976743B), that is, in the process of making solar cells, the doping layers of different polarities are partially contacted, thereby effectively reducing the reverse voltage at both ends of the shielded solar cell, reducing heat generation, and weakening the hot spot effect. After adopting this method, the control of the hot spot effect can be moved forward to the end of the solar cell. Therefore, how to evaluate the hot spot effect at the end of the solar cell has become a technical problem that needs to be solved by those skilled in the art.

[0003] On the other hand, conventional hot spot effect testing generally involves shielding any one or more solar cells (or sub-cells) in a solar cell module, while allowing other solar cells (or sub-cells) to receive light. After a certain period of time, the temperature of the shielded solar cell sub-cell is tested to characterize the hot spot effect. This is obviously not suitable for testing the hot spot effect at the solar cell end. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a back-contact solar cell, a component and a photovoltaic system, which can realize quantitative evaluation of hot spot effect at the cell end.

[0005] In order to solve the above problems, the present invention discloses a back contact solar cell, which comprises:

[0006] The silicon substrate comprises a light-receiving surface and a light-receiving surface which are arranged opposite to each other; and has a first edge and a second edge in a second direction;

[0007] A plurality of first doping layers and a plurality of second doping layers are arranged on the backlight surface, the plurality of first doping layers and the plurality of second doping layers are alternately arranged along a first direction and extend along a second direction; the second doping layers are in composite contact with the first doping layers at a preset position to form a leakage composite contact structure; the first direction intersects with the second direction;

[0008] a plurality of positive electrode grid lines and a plurality of negative electrode grid lines, wherein the positive electrode grid lines are arranged on the first doping layer, and the negative electrode grid lines are arranged on the second doping layer; and

[0009] at least one set of first PAD portions, so that current is passed through the first PAD portions and flows through the leakage composite contact structure;

[0010] Each group of first PAD portions includes a first PAD point and a second PAD point, the first PAD point is electrically connected to at least one of the positive gate lines, and the second PAD point is electrically connected to at least one of the negative gate lines;

[0011] The positive gate line electrically connected to the first PAD point extends along the second direction, and the extension distance is l1; the distance between the first edge and the second edge is L, l1 / L≥0.9;

[0012] The negative electrode grid line electrically connected to the second PAD point extends along the second direction, and the extension distance thereof is l2; l2 / L≥0.9.

[0013] As an improvement of the above technical solution, it includes: the relative distance between the first PAD point and the second PAD point in the second direction is l3, 0.9≤l1 / l3<1, 0.9≤l2 / l3<1.

[0014] As an improvement of the above technical solution, the first PAD point is arranged at the first edge, and the second PAD point is arranged at the second edge.

[0015] As an improvement of the above technical solution, it includes 1 to 12 groups of first PAD parts.

[0016] As an improvement of the above technical solution, the back contact solar cell meets the following relationship:

[0017]

[0018] Among them, U rev is the reverse breakdown voltage of the back contact solar cell, U rev0 is the test reverse voltage of the back-contact solar cell, x is the total number of positive and negative grid lines, x0 is a variable characterizing the first PAD part, x1 is the number of the first PAD points, x2 is the number of the second PAD points, A is a constant ranging from 0.1 to 3.3, and B is a constant ranging from 2 to 50.

[0019] As an improvement of the above technical solution, when multiple first PAD parts are provided, multiple first PAD points are evenly distributed along the first direction; multiple second PAD points are evenly distributed along the first direction.

[0020] As an improvement of the above technical solution, it also includes:

[0021] a first shunt gate line and a second shunt gate line, wherein the first shunt gate line is electrically connected to a plurality of the positive gate lines, and the second shunt gate line is electrically connected to a plurality of the negative gate lines;

[0022] The first shunt gate line is electrically connected to the first PAD point, and the second shunt gate line is electrically connected to the second PAD point.

[0023] As an improvement of the above technical solution, the first shunt gate line is arranged at the first edge, and the positive gate line and the negative gate line are arranged on the side of the first shunt gate line facing the second edge;

[0024] The second shunt gate line is arranged at the second edge, and the positive gate line and the negative gate line are arranged on the side of the second shunt gate line facing the first edge.

[0025] As an improvement of the above technical solution, no gate line is arranged between the first shunt gate line and the first edge;

[0026] No gate line is arranged between the second shunt gate line and the second edge.

[0027] As an improvement of the above technical solution, the width of the first shunt gate line is greater than the width of the positive gate line, and the width of the second shunt gate line is greater than the width of the negative gate line.

[0028] As an improvement of the above technical solution, the distance between the first PAD point and the first edge is greater than the distance between the first shunt gate line and the first edge;

[0029] The distance between the second PAD point and the second edge is greater than the distance between the second shunt gate line and the second edge.

[0030] As an improvement of the above technical solution, the distance between the first PAD point and the first edge is 3 mm to 5 mm; the distance between the second PAD point and the second edge is 3 mm to 5 mm;

[0031] The distance between the first shunt gate line and the first edge is 0.2 mm to 2 mm, and the distance between the second shunt gate line and the second edge is 0.2 mm to 2 mm.

[0032] As an improvement of the above technical solution, the first PAD point is electrically connected to the first shunt gate line through a first connecting gate line;

[0033] The second PAD point is electrically connected to the second shunt gate line through a second connecting gate line.

[0034] As an improvement of the above technical solution, the first connecting grid line is located on an extension line of a positive grid line to the first edge;

[0035] The second connecting grid line is located on an extension line of a negative grid line toward the second edge.

[0036] As an improvement of the above technical solution, the positive electrode grid line includes a first positive electrode sub-grid line, and the first PAD point is provided at an end of the first positive electrode sub-grid line and is electrically connected to the first positive electrode sub-grid line;

[0037] The negative electrode grid line includes a first negative electrode sub-grid line, and the second PAD point is arranged at the end of the first negative electrode sub-grid line and is electrically connected to the first negative electrode sub-grid line;

[0038] The first positive sub-gate line is disposed adjacent to the first negative sub-gate line.

[0039] As an improvement of the above technical solution, the first PAD point is electrically connected to at least three first positive sub-grid lines.

[0040] The second PAD point is electrically connected to at least three first negative electrode sub-grid lines.

[0041] As an improvement of the above technical solution, at least one side of the first connecting grid line in the first direction is further provided with a second negative sub-grid line extending along the second direction, and the second negative sub-grid line is electrically connected to at least one negative grid line close to the first PAD point and is insulated from the first PAD point; and / or

[0042] A second positive sub-grid line extending along the second direction is further provided on at least one side of the second connection grid line in the first direction. The second positive sub-grid line is electrically connected to at least one positive grid line close to the second PAD point and is insulated from the second PAD point.

[0043] As an improvement of the above technical solution, the second negative pole sub-gate line is located on an extension line of the first negative pole sub-gate line connected to the second PAD point toward the first edge; and / or

[0044] The second positive gate line is located on an extension line of the first positive sub-gate line connected to the first PAD point toward the second edge.

[0045] As an improvement of the above technical solution, the first PAD point and the second PAD point are square, circular, triangular or irregular in shape.

[0046] As an improvement of the above technical solution, the first PAD point and the second PAD point are square, and their width is 0.1 mm to 1 mm.

[0047] As an improvement of the above technical solution, it also includes:

[0048] At least one group of second PAD parts, which includes a plurality of third PAD points and a fourth PAD point; the third PAD point is electrically connected to at least one positive electrode grid line and insulated from the negative electrode grid line; the fourth PAD point is electrically connected to at least one negative electrode grid line and insulated from the positive electrode grid line;

[0049] The positive gate line electrically connected to the third PAD point extends along the second direction, and the extension distance is l4; and l4 / L≤0.1;

[0050] The negative electrode grid line electrically connected to the fourth PAD point extends along the second direction, and the extension distance is l5, and l5 / L≤0.1.

[0051] As an improvement of the above technical solution, the silicon substrate has a third edge or a fourth edge arranged opposite to each other in the first direction;

[0052] The second PAD portion is disposed at the third edge and the fourth edge.

[0053] As an improvement of the above technical solution, the geometric center of the third PAD point closest to the first edge and the geometric center of the first PAD point located at the first edge are located on the same straight line extending along the first direction and located on the backlight surface;

[0054] A geometric center of a fourth PAD point closest to the second edge and a geometric center of a second PAD point located at the second edge are located on the same straight line extending along the first direction and located on the backlight surface.

[0055] Correspondingly, the present invention also discloses a battery string, which includes the above-mentioned back-contact solar cell.

[0056] Correspondingly, the present invention also discloses a battery assembly, which includes the above-mentioned back-contact solar cell or the above-mentioned battery string.

[0057] Correspondingly, the present invention also discloses a photovoltaic system, which includes the above-mentioned battery assembly.

[0058] The implementation of the present invention has the following beneficial effects:

[0059] The back-contact solar cell of the present invention includes a plurality of first doped layers and a plurality of second doped layers arranged on the back of a silicon substrate, wherein the second doped layers are in composite contact with the first doped layers at a preset position to form a leakage composite contact structure; in addition, at least one group of first PAD parts is also provided on the backlight surface of the silicon substrate, each group of first PAD parts includes a first PAD point and a second PAD point, the first PAD point is electrically connected to at least one positive grid line, and the second PAD point is electrically connected to at least one negative grid line. Based on the technical solution of this embodiment, a reverse current can be introduced through the first PAD point and the second PAD point, and flows through the leakage composite contact structure, and then the reverse breakdown voltage of the back-contact solar cell can be tested, which provides a good basis for characterizing the hot spot effect at the battery end. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 is a schematic diagram of the composition of a photovoltaic system in one embodiment of the present invention;

[0061] Figure 2 is a schematic structural diagram of a back-contact solar cell assembly according to an embodiment of the present invention;

[0062] Figure 3 is a schematic structural diagram of a back-contact solar cell string according to an embodiment of the present invention;

[0063] Figure 4 is a schematic structural diagram of a back-contact solar cell string in another embodiment of the present invention;

[0064] Figure 5 is a schematic structural diagram of a back-contact solar cell in one embodiment of the present invention;

[0065] Figure 6 is a schematic diagram of the structure of the first doping layer and the second doping layer in one embodiment of the present invention;

[0066] Figure 7 is a schematic cross-sectional structure diagram of a back-contact solar cell in one embodiment of the present invention;

[0067] In the figure, 100 is a battery assembly, 110 is a battery string, 120 is a bus bar, 111 is a back contact solar cell, 112 is a welding strip, 1 is a silicon substrate, 11 is a light receiving surface, 12 is a back light surface, 13 is a first edge, 14 is a second edge, 15 is a third edge, 16 is a fourth edge, 21 is a first doping layer, 22 is a second doping layer, 23 is a spacing area, 24 is a leakage composite contact structure, 25 is a preset position, 31 is a positive grid line, 311 is a positive grid line, is the first positive sub-grid line, 312 is the second positive sub-grid line, 32 is the negative sub-grid line, 321 is the first negative sub-grid line, 322 is the second negative sub-grid line, 40 is the insulating layer, 41 is the first hole, 42 is the second hole, 51 is the first PAD point, 52 is the second PAD point, 61 is the first shunt grid line, 62 is the second shunt grid line, 71 is the first connecting grid line, 72 is the second connecting grid line, 81 is the third PAD point, and 82 is the fourth PAD point. DETAILED DESCRIPTION

[0068] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. In addition, it should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0069] In the description of the present application, it should be understood that the terms "length", "width", "up", "down", "left", "right", "horizontal", "top", "bottom", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0070] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0071] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0072] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0073] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, and does not indicate the relationship between the various embodiments and / or settings discussed in itself. In addition, the various specific processes and examples of materials provided in the present application, but those of ordinary skill in the art can be aware of the application of other processes and / or the use scenarios of other materials.

[0074] refer to Figure 1 The photovoltaic system in one embodiment of the present invention includes the battery assembly 100 in one embodiment of the present application. Multiple battery assemblies 100 can be connected in series or in parallel through a junction box to form a photovoltaic system. The photovoltaic system can be used in photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., and can also be used in equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, solar buildings, etc., but not limited to these.

[0075] See also Figure 2, the battery assembly 100 in one embodiment of the present invention includes at least one battery string 110 in one embodiment of the present invention or at least one back-contact solar cell 111 in one embodiment of the present invention. Preferably, in one embodiment, the battery assembly 100 is composed of a plurality of the above-mentioned battery strings 110, exemplarily 2 strings, 4 strings, 6 strings or 12 strings, but not limited thereto. A plurality of battery strings 110 may be connected in series or in parallel via a bus bar 120, a welding ribbon 112 or other conductive media to form a battery assembly 100. In addition, in order to mechanically connect a plurality of battery strings 110 and meet other use requirements of the assembly (such as electrical connection of a plurality of battery assemblies 100, weather resistance, etc.), it is also necessary to introduce components such as insulating glue, junction boxes, frames, back panels, adhesive films, glass, etc., but not limited thereto.

[0076] refer to Figure 3 and Figure 4 The cell string 110 in one embodiment of the present invention includes a plurality of back-contact solar cells 111 in one embodiment of the present invention, or slices formed by cutting the back-contact solar cells 111. Figure 3 Adjacent back-contact solar cells 111 (or their segments) can be overlapped to form a cell string 110, and connected in series or in parallel through a soldering ribbon 112 or a conductive adhesive, but the invention is not limited thereto. Figure 4 , adjacent back-contact solar cells 111 (or their segments) can be connected in series or in parallel through solder strips 112 and conductive adhesive, but not limited to this. Correspondingly, since the backlight surface 12 of the back-contact solar cell 111 is provided with a positive grid line 31 and a negative grid line 32, in order to prevent the solder strip 112 from short-circuiting the two, it is also necessary to introduce insulating glue or insulating blocks, but not limited to this. In order to meet the fixation of the solder strip 112, it is also necessary to introduce adhesive glue (exemplary such as UV glue), solder paste, etc. In order to achieve the fixation of the back-contact solar cell of the battery string 110, adhesive glue, etc. will also be introduced, but not limited to this.

[0077] Specifically, refer to Figure 5 An embodiment of the present invention discloses a back-contact solar cell 111, which includes: a silicon substrate 1, a plurality of first doped layers 21, a plurality of second doped layers 22, a plurality of positive electrode grid lines 31, and a plurality of negative electrode grid lines 32. The silicon substrate 1 may be P-type monocrystalline silicon, N-type monocrystalline silicon, P-type polycrystalline silicon, or N-type polycrystalline silicon, but is not limited thereto, and is preferably N-type monocrystalline silicon. The silicon substrate 1 includes a light-receiving surface 11 and a backlight surface 12 arranged opposite to each other.

[0078] The first doping layer 21 and the second doping layer 22 are arranged on the backlight surface 12. Specifically, the first doping layer 21 and the second doping layer 22 are arranged alternately along the first direction and extend along the second direction. A spacing region 23 is provided between the first doping layer 21 and the second doping layer 22 to achieve insulation between the first doping layer 21 and the second doping layer 22. The first doping layer 21 may be one or more of a P-type doped polysilicon layer, a P-type doped amorphous silicon layer or a P-type doped microcrystalline silicon layer, but not limited thereto. Preferably, the first doping layer 21 is a P-type polycrystalline silicon layer; the P-type doping element in the first doping layer 21 may be B, Al or Ga, but not limited thereto, preferably B. The second doping layer 22 is an N-type doped polycrystalline silicon layer, an N-type doped amorphous silicon layer or an N-type doped microcrystalline silicon layer, but not limited thereto. Preferably, it is an N-type doped polycrystalline silicon layer. The N-type doping element in the second doping layer 22 may be P, As or Sb, but not limited thereto. Preferably, it is P.

[0079] The first direction intersects with the second direction. Specifically, the first direction may be a vertical direction, and the second direction may be a horizontal direction, but is not limited thereto.

[0080] For details, see Figure 6 In this embodiment, at least one second doping layer 22 is in composite contact with the first doping layer 21 at a preset position 25 to form a leakage composite contact structure 24. Based on the leakage composite contact structure 24, the reverse voltage across the back-contact solar cell 111 under peak current can be reduced, the heat generation power can be reduced, the probability of hot spots occurring can be reduced, and the temperature of the hot spot area when hot spots occur can be reduced.

[0081] Specifically, in one embodiment, at the preset position 25, the first doping layer 21 or the second doping layer 22 can be extended to the doping layer of another polarity (such as the second doping layer 22 or the first doping layer 21), so that the two are in contact to form a leakage composite contact structure 24. In another embodiment, at the preset position 25, a functional layer with a conductive effect is formed so that the first doping layer 21 and the second doping layer 22 are in contact to form a leakage composite contact structure 24. In another embodiment, the leakage composite contact structure 24 can be formed by a stacked structure of the first doping layer 21 and the second doping layer 22. Specifically, the second doping layer 22 can be stacked on the first doping layer 21, or the first doping layer 21 can be stacked on the second doping layer 22. It should be noted that when a stacked structure is adopted, a dielectric layer can also be provided between the first doping layer 21 and the second doping layer 22. The dielectric layer can be a film layer with a tunneling effect, such as a silicon oxide tunneling passivation layer, but is not limited thereto. Preferably, at the preset position 25, the second doping layer 22 is stacked on the first doping layer 21 to form a leakage composite contact structure 24. Based on this structure, the leakage composite contact structure 24 can be formed by etching the second doping layer 22, which is simple in process and highly reliable.

[0082] The positive electrode grid line 31 may be a silver grid line, an aluminum grid line, a copper grid line or a silver-clad copper grid line, but is not limited thereto. The positive electrode grid line 31 is disposed above the first doping layer 21 and contacts the first doping layer 21. Figure 7 In one embodiment, an insulating layer 40 is further provided between the positive gate line 31 and the first doped layer 21. The positive gate line 31 contacts the first doped layer 21 through a first hole 41 provided on the insulating layer 40. The first hole 41 can be formed by a laser process, an etching process, or a slurry burn-through process, but is not limited thereto.

[0083] The negative electrode grid wire 32 may be a silver grid wire, an aluminum grid wire, a copper grid wire or a silver-clad copper grid wire, but is not limited thereto. Figure 7 In one embodiment, an insulating layer 40 is further provided between the negative electrode grid line 32 and the second doping layer 22, and the negative electrode grid line 32 contacts the second doping layer 22 through a second hole 42 provided on the insulating layer 40. The second hole 42 can be formed by a laser process, an etching process, or a slurry burn-through process, but is not limited thereto.

[0084] refer to Figure 5 In this embodiment, the back-contact solar cell 111 includes at least one group of first PAD parts, and each group of first PAD parts includes a first PAD point 51 and a second PAD point 52, and then the reverse current is injected into the back-contact solar cell 111 through the first PAD point 51 and the second PAD point 52, and flows through the leakage composite contact structure 24, and then the reverse breakdown voltage of the back-contact solar cell 111 is tested, which provides a good basis for characterizing the hot spot effect at the battery end. It should be noted that conventional hot spot tests are generally performed at the component end, that is, any one or more solar cell slices in the solar cell component are blocked, and other solar cells (or slices) are exposed to light. After a period of time, the temperature of the blocked solar cell (or slice) is tested to characterize the hot spot effect. It is difficult for the existing technology to accurately quantify the hot spot effect at the battery end. After introducing the leakage composite contact structure 24, this embodiment measures its reverse breakdown voltage, which fully expresses the influence of the leakage composite contact structure 24 on the reverse breakdown voltage, and then quantitatively characterizes the hot spot effect through the reverse breakdown voltage, providing a good basis for controlling the hot spot effect of the component.

[0085] It is understandable that the first PAD point 51 and the second PAD point 52 do not contact the first doping layer 21 and the second doping layer 22 thereunder to prevent leakage. That is, an insulating layer 40 is provided between the first PAD point 51 and the second PAD point 52 and the first doping layer 21 and the second doping layer 22. The insulating layer 40 may include one or more of an aluminum oxide layer, an amorphous silicon layer, a silicon oxide layer, and a silicon nitride layer.

[0086] Among them, the positive gate line 31 electrically connected to the first PAD point 51 extends along the second direction, and its extension distance is l1; the distance between the first edge 13 and the second edge 14 is L, l1 / L≥0.9; the negative gate line 32 electrically connected to the second PAD point 52 extends along the second direction, and its extension distance is l2; l2 / L≥0.9. By controlling the extension distance, the reverse current can flow more through the leakage composite contact structure 24 at the preset position 25, thereby more accurately characterizing the effect of the leakage composite contact structure 24 on the reverse breakdown voltage and evaluating the hot spot effect. At the same time, by controlling the ratio, the back contact solar cell 111 can collect more photogenerated carriers during use, thereby improving its conversion efficiency.

[0087] Exemplarily, l1 / L is 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 or 0.99, but not limited thereto. Preferably, it is 0.93 to 0.95. Exemplary l2 / L is 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 or 0.99, but not limited thereto. Preferably, it is 0.93 to 0.95.

[0088] Preferably, in one embodiment, the relative distance between the first PAD point 51 and the second PAD point 52 in the second direction is l3, 0.9≤l1 / l3<1, 0.9≤l2 / l3<1, so as to further improve the accuracy of testing the reverse breakdown voltage, and further improve the collection efficiency of carriers, and improve the conversion efficiency of the back contact solar cell 111. Exemplarily, l1 / l3 is 0.93, 0.95, 0.96, 0.97, 0.98 or 0.99, but not limited thereto. Preferably, it is 0.97-0.99. Exemplarily, l2 / l3 is 0.93, 0.95, 0.96, 0.97, 0.98 or 0.99, but not limited thereto. Preferably, it is 0.97-0.99. It should be noted that the relative distance between the first PAD point 51 and the second PAD point 52 in the second direction in this embodiment refers to the projection distance of the geometric centers of the two in the second direction.

[0089] Specifically, the first PAD point 51 and the second PAD point 52 are square, circular, triangular or irregular, but not limited thereto. Preferably, in one embodiment, the first PAD point 51 and the second PAD point 52 are square, and their width is 0.1mm to 1mm. Based on this width, the first PAD point 51 and the second PAD point 52 can form good contact with the test probe of the test device. Among them, the test probe refers to the probe used to inject current in the test equipment.

[0090] Specifically, in this embodiment, the first PAD part can be 1 group or multiple groups. It can be understood that when the number of groups is large, the test result of the reverse breakdown voltage is more accurate, but more first test points also mean that more backlight surface 12 area is occupied, and the area for arranging positive gate lines 31 and negative gate lines 32 becomes smaller, which is not good for conversion efficiency. Preferably, considering the conversion efficiency and test accuracy, the number of first PAD parts is set to 1 to 12 groups, exemplarily 1 group, 3 groups, 5 groups, 7 groups or 9 groups, but not limited thereto. Preferably, 1 to 4 groups.

[0091] The influence of the number of the first PAD parts on the reverse breakdown voltage test results is further described below:

[0092] For an ideal diode, the current can be calculated as follows:

[0093]

[0094] In the formula, I DD is the current flowing from the positive electrode to the negative electrode in an ideal diode, I s is the reverse saturation current of the ideal diode; n is the emission coefficient, which is 1 to 2; k is the Boltzmann constant, T is the temperature, q is the space electron charge, and V is the voltage across the positive and negative electrodes of the ideal diode.

[0095] After the leakage composite contact structure 24 is introduced, the current of the diode with leakage current can be calculated by the following formula:

[0096]

[0097] Among them, I D is the output current of the diode with leakage current, I DD is the current flowing from the positive electrode to the negative electrode in an ideal diode, I S is the reverse saturation current of the ideal diode, n is the emission coefficient, which is 1 to 2; k is the Boltzmann constant, T is the temperature, q is the space electron charge, V is the voltage across the positive and negative electrodes of the diode, I S,R is the reverse saturation current of the diode with leakage current, n R is the leakage emission coefficient, n R ≥2.

[0098] Under non-ideal conditions, the diode can be reversely broken down, and the reverse breakdown current I DBR It can be expressed as:

[0099]

[0100] Among them, I BR is the breakdown inflection point current; V is the voltage across the positive and negative electrodes of the diode, VBR is the reverse breakdown voltage, n BR is the breakdown emission coefficient, and its value range is 0.95~1.02.

[0101] Therefore, when the series resistance (ie, the gate line resistance and the contact resistance between the gate line and the doping layer) is not taken into account, the current in the back contact solar cell 111 of this embodiment can be calculated by the following formula:

[0102]

[0103] In actual testing, due to the voltage division of series resistance (gate line resistance, contact resistance between gate line and doping layer), when the external voltage is V W When the line resistance of a pitch (PN unit) gate line transmission is R s , x is the number of pitches through which the transmission current passes, and the gate line has good contact with the doped layer, and the contact resistance is extremely small, then the voltage across the minimum unit diode is V = V w -xI D R s .

[0104] Then, after taking into account the series resistance, the current of a single PN unit in the back contact battery in this embodiment can be calculated by the following formula:

[0105]

[0106] Where V W is the applied voltage, R s is the line resistance of the gate line transmission of a pitch (PN unit), x is a variable representing the number of pitches between the positive gate line 31 and the first PAD point 51, and Figure 6 For example, there are 6 first doping layers 21 and 6 second doping layers 22 between adjacent first PAD points 51 / second PAD points 52 , for a total of 6 PN units, then x=6÷2=3.

[0107] Here, it should be noted that in this embodiment, a plurality of first doping layers 21 and second doping layers 22 are arranged on the back of the back contact cell, which together with the silicon substrate 11 form a plurality of PN units, and it can be approximately considered that the plurality of PN units are connected in parallel.

[0108] Therefore, when only one set of the first PAD portion is provided on the back contact solar cell 111 having z PN units (pitch), the measured current and voltage can be calculated by the following formula:

[0109]

[0110] Among them, I D2 is the current measured when setting a first PAD part, V C2is the voltage measured when a group of first PAD parts is set.

[0111] If four first PADs are set, the measured current and voltage can be calculated by the following formula:

[0112]

[0113] Among them, I D5 is the current measured when setting the first PAD part of the four groups, V C5 It is the voltage measured when four groups of the first PAD parts are set.

[0114] From the above two equations, we can undoubtedly find that: D5 >I D2 Therefore, for the same back-contact solar cell 111 to be tested, V C5 <V C2 . That is, when the first PAD part is increased, the test result of the reverse breakdown voltage is more accurate. In addition, increasing the number of test points can reduce the test error caused by the first shunt gate line 61 / the second shunt gate line 62 and other broken gates. However, as mentioned above, increasing the first test point is not conducive to the improvement of conversion efficiency. To this end, the inventors have conducted a large number of tests based on the above analysis and proposed a specific correction method. Specifically, in one embodiment of the present invention, the back contact solar cell 111 meets the following relationship:

[0115]

[0116] Among them, U rev is the reverse breakdown voltage of the back contact solar cell 111, U rev0 is the test reverse voltage of the back-contact solar cell 111, x is the total number of positive grid lines 31 and negative grid lines 32, x0 is a variable characterizing the first PAD portion, x1 is the number of first PAD points 51, x2 is the number of second PAD points 52, A is a constant, and its value range is 0.1 to 3.3, and B is a constant, and its value range is 2 to 50.

[0117] Based on the above relationship, when setting any group of first PAD parts, the test results can be corrected to obtain an accurate reverse breakdown voltage. Specifically, it is found that when 1 to 4 groups of first PAD parts are set, the test error is ≤5%, when 4 to 6 groups are set, the test error is ≤3.5%, and when 8 to 10 groups are set, the test error is ≤1.5%.

[0118] In one embodiment, when multiple first PAD portions are provided, multiple first PAD points 51 are evenly distributed along the first direction, which facilitates even distribution of the test current and avoids the phenomenon of high reverse breakdown voltage during the test. Correspondingly, multiple second PAD points 52 are also evenly distributed along the first direction.

[0119] Among them, in one embodiment, the first PAD point 51 is set at the first edge 13, and the second PAD point 52 is set at the second edge 14. It should be noted that there are line resistances in the positive gate line 31 and the negative gate line 32. After the reverse current is passed, there will be voltage division on these gate lines; in addition, there are contact resistances between the positive gate line 31 and the first doped layer 21, and between the negative gate line 32 and the second doped layer 22, which will also produce voltage division. Therefore, in order to more accurately characterize the reverse breakdown voltage of the back contact solar cell 111, it is necessary to consider the gate line resistance voltage division and the contact resistance voltage division. In this embodiment, the first PAD point 51 and the second PAD point 52 are set at the edge of the silicon substrate 1 in the second direction, and the positive gate line 31 and the negative gate line 32 are extended along the second direction. Therefore, in this embodiment, the reverse current can flow through the longer positive gate line 31 and the negative gate line 32 in the second direction, which can better characterize the influence of the gate line resistance voltage division and the contact resistance voltage division on the reverse breakdown voltage.

[0120] It is understood that, in this embodiment, the first PAD point 51 is disposed at the first edge 13, which means that it is disposed close to the first edge 13. Specifically, the distance between the first PAD point 51 and the first edge 13 is 1 mm to 10 mm, exemplarily 1.5 mm, 3 mm, 4.5 mm, 6 mm, 7.5 mm, or 9 mm, but not limited thereto. Specifically, the distance between the first PAD point 51 and the first edge 13 refers to the distance between the geometric center of the first PAD point 51 and the first edge 13.

[0121] It is understood that, in this embodiment, the second PAD point 52 is disposed at the second edge 14, which means that it is disposed close to the second edge 14. Specifically, the distance between the second PAD point 52 and the second edge 14 is 1 mm to 10 mm, exemplarily 1.5 mm, 3 mm, 4.5 mm, 6 mm, 7.5 mm or 9 mm, but not limited thereto. Specifically, the distance between the second PAD point 52 and the second edge 14 refers to the distance between the geometric center of the second PAD point 52 and the second edge 14.

[0122] Specifically, in one embodiment, the back-contact solar cell 111 also includes a first shunt gate line 61 and a second shunt gate line 62, the first shunt gate line 61 is electrically connected to a plurality of positive gate lines 31, and the second shunt gate line 62 is electrically connected to a plurality of negative gate lines 32; the first shunt gate line 61 is electrically connected to the first PAD point 51, and the second shunt gate line 62 is electrically connected to the second PAD point 52; based on the above embodiment, the reverse current from the second PAD point 52 is shunted to the plurality of negative gate lines 32 via the second shunt gate line 62, and then flows through the plurality of positive gate lines 31 and is then collected to the first PAD point 51 via the first shunt gate line 61, thereby achieving the effect of better characterizing the influence of gate line resistance voltage division and contact resistance voltage division on the accuracy of the reverse breakdown voltage test. In addition, it should be noted that: when the number of groups of the first PAD points 51 set is small, the number of PN units passing through will also be reduced accordingly. Although this test value can also characterize the hot spot effect of the back-contact solar cell 111 to a certain extent, it is not accurate enough. By introducing the first shunt gate line 61 and the second shunt gate line 62, the reverse current can flow through more PN units, thereby effectively improving the accuracy of the test.

[0123] The first shunt grid line 61 and the second shunt grid line 62 may be in a straight line or a curved line, and may be arranged parallel to the first direction or at an angle with the first direction, but are not limited thereto. Preferably, in one embodiment, the first shunt grid line 61 and the second shunt grid line 62 are in a straight line and extend along the first direction, that is, they are parallel to the first direction, which reduces the length of the first shunt grid line 61 and the second shunt grid line 62 between the positive grid line 31 to be connected or the negative grid line 32 to be connected, and simplifies the grid line arrangement.

[0124] Preferably, in one embodiment, the width of the first shunt grid line 61 is controlled to be greater than the width of the positive grid line 31, and the width of the second shunt grid line 62 is controlled to be greater than the width of the negative grid line 32, so as to reduce the current loss of the first shunt grid line 61 and the second shunt grid line 62, especially when the number of groups of the first PAD part is small, it can prevent the first shunt grid line 61 and the second shunt grid line 62 from consuming too much current, ensure that the test current is dispersed to more positive grid lines 31 and negative grid lines 32 through the first shunt grid line 61 / the second shunt grid line 62, and improve the test accuracy. More preferably, the width of the first shunt grid line 61 is 1.5 to 3 times the width of the positive grid line 31, and the width of the second shunt grid line 62 is 1.5 to 3 times the width of the negative grid line 32.

[0125] Among them, in one embodiment, the first shunt gate line 61 is arranged at the first edge 13, and the second shunt gate line 62 is arranged at the second edge 14. Based on this arrangement, the gate line structure can be simplified, the carrier collection efficiency can be improved, and the conversion efficiency can be improved. Since the first shunt gate line 61 / the second shunt gate line 62 connects a plurality of positive gate lines 31 / negative gate lines 32 extending in the second direction, if the first shunt gate line 61 / the second shunt gate line 62 is arranged in the center, a plurality of discontinuous insulation structures or other types of insulation structures need to be arranged in the gate line regions with different polarities, and the gate line structure is complicated, and the arrangement area of ​​the positive gate line 31 and the negative gate line 32 is reduced, thereby reducing the collection of carriers.

[0126] It can be understood that, in this embodiment, the first shunt gate line 61 is disposed at the first edge 13, which means that it is disposed close to the first edge 13. Specifically, the distance between the first shunt gate line 61 and the first edge 13 is 0.1 mm to 3 mm, exemplarily 0.5 mm, 1 mm, 1.5 mm, 2 mm or 2.5 mm, but not limited thereto. Specifically, the distance between the first shunt gate line 61 and the first edge 13 refers to the distance between the center line of the first shunt gate line 61 and the first edge 13.

[0127] It can be understood that, in this embodiment, the second shunt grid line 62 is disposed at the second edge 14, which means that it is disposed close to the second edge 14. Specifically, the distance between the second shunt grid line 62 and the second edge 14 is 0.1 mm to 3 mm, exemplarily 0.5 mm, 1 mm, 1.5 mm, 2 mm or 2.5 mm, but not limited thereto. Specifically, the distance between the second shunt grid line 62 and the second edge 14 refers to the distance between the center line of the second shunt grid line 62 and the second edge 14.

[0128] Preferably, in one embodiment, the first shunt grid line 61 is arranged at the end of the positive grid line 31 close to the first edge 13, that is, the positive grid line 31 and the negative grid line 32 are arranged on the side of the first shunt grid line 61 facing the second edge 14; and no other grid lines are arranged between the first shunt grid line 61 and the first edge 13. Based on the above arrangement, the carrier collection area can be widened and the conversion efficiency of the back contact solar cell 111 can be improved. In addition, the accuracy of the reverse breakdown voltage can also be improved.

[0129] Correspondingly, in one embodiment, the second shunt gate line 62 is arranged at the end of the negative gate line 32 close to the second edge 14, that is, the positive gate line 31 and the negative gate line 32 are arranged on the side of the second shunt gate line 62 facing the first edge 13, and no other gate lines are arranged between the second shunt gate line 62 and the second edge 14 to improve conversion efficiency and test accuracy.

[0130] It can be expected that since the first shunt grid line 61 and the second shunt grid line 62 are arranged close to the edge of the back-contact solar cell 111, the photogenerated carriers at the edge are relatively few; and the first shunt grid line 61 and the second shunt grid line 62 extend along the first direction, if the openings thereof are in contact with the doping layer of the corresponding polarity, more recombination losses will be introduced, therefore, the first shunt grid line 61 and the second shunt grid line 62 region do not have openings in contact with the doping layer, and they only play the role of shunt / convergence. At the same time, it can be understood that by increasing the number of the first PAD point 51 and the second PAD point 52, the influence of the first shunt grid line 61 / the second shunt grid line 62 broken gate on the test results can also be reduced.

[0131] Specifically, in one embodiment, when the first PAD point 51 and the first shunt gate line 61 are both set at the first edge 13, the distance between the first PAD point 51 and the first edge 13 is controlled to be greater than the distance between the first shunt gate line 61 and the first edge 13. Since the first PAD point 51 is relatively large and too close to the edge of the silicon substrate 1, it is easy to cause defects such as hidden cracks during printing. Moreover, by controlling the first shunt gate line 61 to be closer to the first edge 13, a spacing area is formed between the first shunt gate line 61 and the first PAD point 51, and a gate line can be set in the spacing area to further improve the collection efficiency of carriers and improve the conversion efficiency. Specifically, based on this embodiment, the distance between the first PAD point 51 and the first edge 13 is controlled to be 3mm to 8mm, and the distance between the first shunt gate line 61 and the first edge 13 is 0.2mm to 5mm.

[0132] Specifically, when a spacing area is formed between the first shunt gate line 61 and the first PAD point 51, the first shunt gate line 61 can be electrically connected to the first PAD point 51 through the first connecting gate line 71. Preferably, in one embodiment, the first connecting gate line 71 extends along the second direction, and the first connecting gate line 71 is located on the extension line of a positive gate line 31 to the first edge 13; that is, the first connecting gate line 71 is arranged above the first doping layer 21 corresponding to the positive gate line 31, and then the first connecting gate line 71 can be connected to the first doping layer 21 through the first hole 41, so that the first connecting gate line 71 can also collect carriers to improve the conversion efficiency.

[0133] Correspondingly, in one embodiment, when the second PAD point 52 and the second shunt gate line 62 are both set at the second edge 14, the distance between the second PAD point 52 and the second edge 14 is controlled to be greater than the distance between the second shunt gate line 62 and the second edge 14. Since the second PAD point 52 is relatively large and too close to the edge of the silicon substrate 1, it is easy to cause defects such as hidden cracks during printing. Moreover, by controlling the second shunt gate line 62 to be closer to the second edge 14, a spacing area is formed between the second shunt gate line 62 and the second PAD point 52, and a gate line can be set in the spacing area to further improve the collection efficiency of carriers and improve the conversion efficiency. Specifically, based on this embodiment, the distance between the second PAD point 52 and the second edge 14 is controlled to be 3mm to 8mm, and the distance between the second shunt gate line 62 and the second edge 14 is 0.2mm to 5mm.

[0134] Specifically, when a spacing area is formed between the second shunt gate line 62 and the second PAD point 52, the second shunt gate line 62 can be electrically connected to the second PAD point 52 through the second connection gate line 72. Preferably, in one embodiment, the second connection gate line 72 extends along the second direction, and the second connection gate line 72 is located on the extension line of a negative gate line 32 to the second edge 14; that is, the second connection gate line 72 is arranged above the second doping layer 22 corresponding to the negative gate line 32, and then the second connection gate line 72 can be connected to the second doping layer 22 through the second hole 42, so that the second connection gate line 72 can also collect carriers to improve the conversion efficiency.

[0135] Specifically, in one embodiment, the positive grid line 31 includes a first positive sub-grid line 311, the negative grid line 32 includes a first negative sub-grid line 321 disposed adjacent to the first positive grid line 31, and the first PAD point 51 is disposed at the end of the first positive sub-grid line 311 close to the first edge 13, and is electrically connected to the first positive sub-grid line 311. The second PAD point 52 is disposed at the end of the first negative sub-grid line 321 close to the second edge, and is electrically connected to the first negative sub-grid line 321. Based on this embodiment, the first PAD point 51 and the second PAD point 52 in each group of the first PAD portion are approximately disposed on the same straight line extending along the second direction, so that the stress distribution during printing is relatively uniform, thereby reducing the risk of cracking.

[0136] Specifically, in one embodiment, the first PAD point 51 is electrically connected to at least three first positive sub-grid lines 311; the second PAD point 52 is electrically connected to at least three first negative sub-grid lines 321. Although the first PAD point 51 / the second PAD point 52 can distribute the reverse current through the first shunt grid line 61 / the second shunt grid line 62, the first shunt grid line 61 / the second shunt grid line 62 is narrow, and when the current density is too large, more current is consumed. For this reason, the first PAD point 51 / the second PAD point 52 is connected to at least three first positive sub-grid lines 311 / the first negative sub-grid lines 321 to optimize the current distribution and improve the test accuracy. More preferably, the first PAD point 51 is electrically connected to the three first positive sub-gate lines 311; the second PAD point 52 is electrically connected to the three first negative sub-gate lines 321. When the number of connected gate lines is too large, the sizes of the first PAD point 51 and the second PAD point 52 are too large, occupying more area of ​​the gate lines for collecting carriers, which is not conducive to improving the conversion efficiency.

[0137] Preferably, in one embodiment, at least one side of the first connecting grid line 71 in the first direction is further provided with a second negative sub-grid line 322 extending in the second direction, the second negative sub-grid line 322 is electrically connected to at least one negative grid line 32 close to the first PAD point 51, and is insulated from the first PAD point 51; through the second negative sub-grid line 322, the carriers in the interval between the first shunt grid line 61 and the first PAD point 51 can be collected to improve the conversion efficiency. More preferably, in order to collect more carriers, the second negative sub-grid line 322 is arranged on the extension line of the first negative sub-grid line 321 connected to the second PAD point 52 to the first edge 13; that is, the second negative sub-grid line 322 is arranged above the second doped layer 22 corresponding to the first negative sub-grid line 321, and then the second negative sub-grid line 322 can be connected to the second doped layer 22 through the second hole 42, so that the second negative sub-grid line 322 can also collect carriers to improve the conversion efficiency.

[0138] Correspondingly, in one embodiment, at least one side of the second connection grid line 72 in the first direction is further provided with a second positive sub-grid line 312 extending in the second direction, and the second positive sub-grid line 312 is electrically connected to at least one positive grid line 31 close to the second PAD point 52, and is insulated from the second PAD point 52. Through the second positive sub-grid line 312, the carriers in the interval between the second shunt grid line 62 and the second test PAD point can be collected to improve the conversion efficiency. More preferably, in order to collect more carriers, the second positive sub-grid line 312 is arranged on the extension line of the first positive sub-grid line 311 connected to the first PAD point 51 to the second edge 14; that is, the second positive sub-grid line 312 is arranged above the first doped layer 21 corresponding to the first positive sub-grid line 311, and then the second positive sub-grid line 312 can be connected to the first doped layer 21 through the first hole 41, so that the second positive sub-grid line 312 can also collect more carriers to improve the conversion efficiency.

[0139] Specifically, in one embodiment, the back-contact solar cell 111 further includes at least one group of second PAD portions, which are mainly used to connect the welding strip 112, so that the back-contact solar cell 111 forms a battery string 110 and a battery assembly 100. Specifically, each group of second PAD portions includes a third PAD point 81 and a fourth PAD point 82, wherein the third PAD point 81 is electrically connected to at least one positive electrode grid line 31 and is insulated from the negative electrode grid line 32. The fourth PAD point 82 is electrically connected to at least one negative electrode grid line 32 and is insulated from the positive electrode grid line 31. That is, the third PAD point 81 is used to connect the positive electrode welding strip 112, and the fourth PAD point 82 is used to connect the negative electrode welding strip 112.

[0140] Among them, the positive grid line 31 electrically connected to the third PAD point 81 extends along the second direction, and its extension distance is l4; optionally, l4 / L≤0.1; based on this ratio, one ensures that the carrier transmission distance is appropriate, reduces the grid line transmission loss, and improves the power of the battery string 110 / battery assembly 100. Both ensure that the third PAD point 81 is reasonably distributed, improve the welding tension, and ensure the reliability of the battery assembly 100. Exemplarily, l4 / L is 0.01, 0.02, 0.04, 0.06 or 0.08, but is not limited thereto. Preferably, l4 / L is 0.06-0.09.

[0141] Among them, the negative electrode grid line 32 electrically connected to the fourth PAD point 82 extends along the second direction, and its extension distance is l5, and l5 / L≤0.1. Based on this ratio, one ensures that the carrier transmission distance is appropriate, reduces the grid line transmission loss, and improves the power of the battery string 110 / battery assembly 100. Both ensure that the fourth PAD point 82 is reasonably distributed, improves the welding tension, and ensures the reliability of the battery assembly 100. Exemplarily, l5 / L is 0.01, 0.02, 0.04, 0.06 or 0.08, but is not limited to this. Preferably, l5 / L is 0.06-0.09.

[0142] Specifically, based on the above embodiment, the number of the third PAD points 81 is 8 to 20, exemplarily 9, 11, 13, 15, 17 or 19, but not limited thereto, and more preferably 12 to 20.

[0143] Accordingly, the number of the fourth PAD points 82 is 8 to 20, exemplarily 9, 11, 13, 15, 17 or 19, but not limited thereto, and more preferably 12 to 20.

[0144] Specifically, when a group of second PAD portions includes a plurality of third PAD points 81 and a plurality of fourth PAD points 82, the third PAD points 81 and the fourth PAD points 82 are alternately arranged along the second direction. Based on this arrangement relationship, the current transmission distance can be further optimized, the loss can be reduced, and the power can be increased. Furthermore, in order to simplify the electrode pattern and reduce the printing stress, the plurality of third PAD points 81 and the fourth PAD points 82 in the same group are arranged in a row in the second direction.

[0145] Specifically, the second PAD portion can be arranged in the middle, at the edge or at any other position of the back contact solar cell 111. Preferably, in one embodiment, the silicon substrate 1 has a third edge 15 and a fourth edge 16 arranged opposite to each other in the first direction, and the second PAD portion is arranged at the third edge 15 and the fourth edge 16. Through this arrangement, the welding tension can be greatly improved to ensure the reliability of the battery string 110 / battery assembly 100.

[0146] It is understandable that in this embodiment, the second PAD portion is arranged at the third edge 15 / fourth edge 16 means that the third PAD point 81 and the fourth PAD point 82 are both arranged close to the third edge 15 / fourth edge 16. More specifically, the distance between the third PAD point 81 / fourth PAD point 82 and the third edge 15 / fourth edge 16 is 1mm to 5mm, exemplarily 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm or 4.5mm, but not limited thereto. It is understandable that the distance between the third PAD point 81 / fourth PAD point 82 and the third edge 15 / fourth edge 16 refers to the distance between the geometric center of the third PAD point 81 / fourth PAD point 82 and the third edge 15 / fourth edge 16.

[0147] Preferably, in one embodiment, the geometric center of the third PAD point 81 closest to the first edge 13 and the geometric center of the first PAD point 51 located at the first edge 13 are located on the same straight line extending along the first direction and located on the backlight surface 12; based on this embodiment, the first PAD point 51 can also be used for welding, which can further increase the welding tension.

[0148] Accordingly, in one embodiment, the geometric center of the fourth PAD point 82 closest to the second edge 14 and the geometric center of the second PAD point 52 located at the second edge 14 are located on the same straight line extending along the first direction and located on the backlight surface 12. Based on this embodiment, the second PAD point 52 can also be used for welding, which can further increase the welding tension.

[0149] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0150] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A back contact solar cell, characterized in that: include: A silicon substrate, comprising a light-receiving surface and a backlight surface that are arranged opposite to each other; It has a first edge and a second edge in a second direction; A plurality of first doping layers and a plurality of second doping layers are arranged on the backlight surface, the plurality of first doping layers and the plurality of second doping layers are alternately arranged along a first direction and extend along a second direction; the second doping layers are in composite contact with the first doping layers at a preset position to form a leakage composite contact structure; the first direction intersects with the second direction; a plurality of positive electrode grid lines and a plurality of negative electrode grid lines, wherein the positive electrode grid lines are arranged on the first doping layer, and the negative electrode grid lines are arranged on the second doping layer; and at least one set of first PAD portions, so that current is passed through the first PAD portions and flows through the leakage composite contact structure; Each group of first PAD portions includes a first PAD point and a second PAD point, the first PAD point is electrically connected to at least one of the positive gate lines, and the second PAD point is electrically connected to at least one of the negative gate lines; The positive gate line electrically connected to the first PAD point extends along the second direction, and the extension distance is l1; the distance between the first edge and the second edge is L, l1 / L≥0.9; The negative electrode grid line electrically connected to the second PAD point extends along the second direction, and the extension distance thereof is l2; l2 / L≥0.

9.

2. The back contact solar cell according to claim 1, characterized in that: include: A relative distance between the first PAD point and the second PAD point in the second direction is l3, 0.9≤l1 / l3<1, 0.9≤l2 / l3<1.

3. The back contact solar cell according to claim 1, characterized in that: The first PAD point is located at the first edge, and the second PAD point is located at the second edge.

4. The back contact solar cell according to claim 1, characterized in that: It includes 1 to 12 groups of first PAD parts.

5. The back contact solar cell according to any one of claims 1 to 4, characterized in that: The back contact solar cell meets the following relationship: Among them, U rev is the reverse breakdown voltage of the back contact solar cell, U rev0 is the test reverse voltage of the back-contact solar cell, x is the total number of positive and negative grid lines, x0 is a variable characterizing the first PAD part, x1 is the number of the first PAD points, x2 is the number of the second PAD points, A is a constant ranging from 0.1 to 3.3, and B is a constant ranging from 2 to 50.

6. The back contact solar cell according to claim 4, characterized in that: When a plurality of first PAD portions are provided, the plurality of first PAD points are evenly distributed along the first direction; and the plurality of second PAD points are evenly distributed along the first direction.

7. The back contact solar cell according to claim 1, characterized in that: Also includes: a first shunt gate line and a second shunt gate line, wherein the first shunt gate line is electrically connected to a plurality of the positive gate lines, and the second shunt gate line is electrically connected to a plurality of the negative gate lines; The first shunt gate line is electrically connected to the first PAD point, and the second shunt gate line is electrically connected to the second PAD point.

8. The back contact solar cell according to claim 7, characterized in that: The first shunt gate line is arranged at the first edge, and the positive gate line and the negative gate line are arranged on a side of the first shunt gate line facing the second edge; The second shunt gate line is arranged at the second edge, and the positive gate line and the negative gate line are arranged on the side of the second shunt gate line facing the first edge.

9. The back contact solar cell according to claim 8, characterized in that: No gate line is arranged between the first shunt gate line and the first edge; No gate line is arranged between the second shunt gate line and the second edge.

10. The back contact solar cell according to claim 7, characterized in that: The width of the first shunt gate line is greater than the width of the positive gate line, and the width of the second shunt gate line is greater than the width of the negative gate line.

11. The back contact solar cell according to claim 7, characterized in that: The distance between the first PAD point and the first edge is greater than the distance between the first shunt gate line and the first edge; The distance between the second PAD point and the second edge is greater than the distance between the second shunt gate line and the second edge.

12. The back contact solar cell according to claim 11, characterized in that: The distance between the first PAD point and the first edge is 3 mm to 5 mm; the distance between the second PAD point and the second edge is 3 mm to 5 mm; The distance between the first shunt gate line and the first edge is 0.2 mm to 2 mm, and the distance between the second shunt gate line and the second edge is 0.2 mm to 2 mm.

13. The back contact solar cell according to claim 7, characterized in that: The first PAD point is electrically connected to the first shunt gate line via a first connecting gate line; The second PAD point is electrically connected to the second shunt gate line through a second connecting gate line.

14. The back contact solar cell according to claim 13, characterized in that: The first connecting grid line is located on an extension line of a positive grid line toward the first edge; The second connecting grid line is located on an extension line of a negative grid line toward the second edge.

15. The back contact solar cell according to claim 13, characterized in that: The positive gate line includes a first positive sub-gate line, and the first PAD point is arranged at an end of the first positive sub-gate line and is electrically connected to the first positive sub-gate line; The negative electrode grid line includes a first negative electrode sub-grid line, and the second PAD point is arranged at the end of the first negative electrode sub-grid line and is electrically connected to the first negative electrode sub-grid line; The first positive sub-gate line is disposed adjacent to the first negative sub-gate line.

16. The back contact solar cell according to claim 15, characterized in that: The first PAD point is electrically connected to at least three first positive sub-grid lines The second PAD point is electrically connected to at least three first negative electrode sub-grid lines.

17. The back contact solar cell according to claim 15, characterized in that: A second negative pole sub-grid line extending along a second direction is further provided on at least one side of the first connecting grid line in the first direction, the second negative pole sub-grid line is electrically connected to at least one negative pole grid line close to the first PAD point, and is insulated from the first PAD point; and / or A second positive sub-grid line extending along the second direction is further provided on at least one side of the second connection grid line in the first direction. The second positive sub-grid line is electrically connected to at least one positive grid line close to the second PAD point and is insulated from the second PAD point.

18. The back contact solar cell according to claim 17, characterized in that: The second negative pole sub-gate line is located on an extension line of the first negative pole sub-gate line connected to the second PAD point toward the first edge; and / or The second positive gate line is located on an extension line of the first positive sub-gate line connected to the first PAD point toward the second edge.

19. The back contact solar cell according to claim 1, characterized in that: The first PAD point and the second PAD point are square, circular, triangular or irregular in shape.

20. The back contact solar cell according to claim 1, characterized in that: The first PAD point and the second PAD point are square in shape, and the width thereof is 0.1 mm to 1 mm.

21. The back contact solar cell according to claim 1, characterized in that: Also includes: At least one group of second PAD parts, which includes a plurality of third PAD points and a fourth PAD point; the third PAD point is electrically connected to at least one positive electrode grid line and insulated from the negative electrode grid line; the fourth PAD point is electrically connected to at least one negative electrode grid line and insulated from the positive electrode grid line; The positive gate line electrically connected to the third PAD point extends along the second direction, and the extension distance is l4; and l4 / L≤0.1; The negative electrode grid line electrically connected to the fourth PAD point extends along the second direction, and the extension distance is l5, and l5 / L≤0.

1.

22. The back contact solar cell according to claim 21, characterized in that: The silicon substrate has a third edge or a fourth edge that is oppositely arranged in the first direction; The second PAD portion is disposed at the third edge and the fourth edge.

23. The back contact solar cell according to claim 22, characterized in that: The geometric center of the third PAD point closest to the first edge and the geometric center of the first PAD point located at the first edge are located on the same straight line extending along the first direction and located on the backlight surface; A geometric center of a fourth PAD point closest to the second edge and a geometric center of a second PAD point located at the second edge are located on the same straight line extending along the first direction and located on the backlight surface.

24. A battery string, characterized in that: Comprising a back-contact solar cell as described in any one of claims 1 to 23.

25. A battery assembly, characterized in that: It comprises the back-contact solar cell according to any one of claims 1 to 23 or the cell string according to claim 24.

26. A photovoltaic system, characterized in that: Comprising a battery assembly as claimed in claim 25.

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